Spatial memory and c-fos expression in supramammillary nucleus, anterior cingulated gyrus and entorhinal cortex

To investigate brain substrates of spatial memory, the cellular expression of c-Fos protein in mts was studied after training the animals to perform a spatial reference memory task and a working reference memory task in a Morris water maze. The number of c-Fos positive neuronal nuclei was quantified in several brain regions: entorhinal cortex, anterior cingulate gyrus, and supramammillary nucleus. The results showed that spatial training in reference and working memory tasks increased the number of entorhinal cortex activated neurons (c-Fos positive neurons). No clear association was found between c-Sos activation in the anterior cingulate gyrus and either spatial reference or working memory tasks. The number of c-Fos immunoreactive neuronal nuclei in the supramammillary neurons was greater in thr spatial working memory groups than in the spatial reference memory groups suggesting that neurons of the supramammillary nucleus plays an important role in spatial processing.